1. Field of the Invention
This specification relates to multifunctional thermal conducting and/or radiating particles and an array having the same, and more particularly, multifunctional thermal conducting and/or radiating particles having not only thermal conductivity but also at least one of various properties, such as electromagnetic wave absorbing property, flame retardency, antistatic property, insulating property, thermal resistance, electrical conductivity and the like, an array having the same and a fabrication method thereof.
2. Background of the Invention
As specific devices, such as flat panel display devices, flexible devices, LEDs, vehicle packages, small-sized electronic devices and information communication devices, become thin in thickness and integrated, countermeasures against heat, electromagnetic waves and the like are being at issue. Especially, a processing speed of a microprocessor as a logical chip device is getting fast up to several GHz, and a memory semiconductor highly increases in capacity up to almost terabit. Accordingly, thermal density is further increased and emission of electromagnetic waves are drastically increased, thereby affecting or being affected by adjacent electronic components or the device itself to cause an electromagnetic interference (EMI/EMC) and thermal aging. Hence, it is urgent to prepare countermeasures against such heat, electromagnetic waves and the like in the latest devices. To solve the thermal problems generated from electronic components or electronic component modules, a heat sink is widely used. The heat sink is attached onto an electronic module acting as a heat source to fast disperse (spread) generated heat to the exterior. When the heat sink is physically attached onto such electronic component, the attached surface is not flat and thereby a gap may be generated therebetween, thereby causing an inefficient heat transfer. In regard of this, to lower thermal resistance at a contact part, a flexible film or a greasy thermal interface material (TIM) is interposed therebetween. Also, the heat sink emits high heat in a high power LED package and the like, complex functions (properties) such as thermal resistance, flame retardency and the like are also required.
However, the conventional TIM has been designed for the purpose of facilitating heat transfer between the electronic component and the heat sink, so it has not had a function of removing radiation noise generated from the inside of an electronic device or electrical noise introduced from the outside.
For preventing noise interference in the related art, electromagnetic waves, which are emitted from the electronic components or introduced from the outside, was blocked by covering the electronic components or blocking a gap using a shielding case, a conductive sheet, a conductive fiber, a conductive gasket, a conductive paste and the like, those formed of a conductive metal (e.g., silver, copper, etc.). Those materials are mainly made of the conductive metal, thus to exhibit superior thermal radiating properties. However, for packaging with electronic components by applying those materials, an electric shock may be caused due to low withstand voltages. Consequently, they are inappropriate as TIM material unless an electrically insulating layer is further inserted.
An electromagnetic wave shielding/absorbing material (JP 2006-135118 A1), which is formed by laminating the electromagnetic wave absorbers, fabricated in the related art in a sheet form, or electromagnetic wave absorbers and conductive shielding materials in a multi-layered structure, exhibits high electromagnetic wave shielding effect but has difficulty in effectively dispersing (spreading, dissipating) heat. In order to satisfy various functions required in electric/electronic devices, various functional materials should be inserted, however, they may not effectively cope with the recent tendency of being thin in thickness. In recent years, several methods have been introduced in which multifunctional thermal radiating materials simultaneously having different functions (properties), such as electromagnetic wave absorbing properties, electrically insulating property, thermal resistance, flame retardency and the like so as to acquire spatial and economical advantages.
As one example, for simultaneous exhibition of electromagnetic wave absorbing property and thermal conductivity, a method, in which magnetic powders and high conductive ceramic powders are mixed with a polymer binder using a typical agitator, followed by extrusion or tape-casting, thereby fabricating a powder composite in a sheet form, has been filed in Europe (EP 1372162A1), Japan (JP 2007-31695) and USA (U.S. Pat. No. 7,030,172 B2). However, upon requirements of two or more functionalities, an appropriate means for formation of a heat transfer path between thermal conductors is not found, for example, in a multifunctional array (structure) using both a filler having relatively low thermal conductivity and a filler having high-thermal conductivity, the fillers having different functions.